he's interviewed by congressman jim heinz. watch book tv every sunday and find a full schedule on your program guide or watch online anytime at booktv.org . >> election day november 8 starting at 8 pm eastern watch c-span's live election night coverage to see which party will control congress. your results as they happen from house, senate and governorraces from around the country . see victory and concession speeches from the candidates on the c-span mobile app and that c-span.org/campaign 2022 . >> there are a lot of places to get political information butonly at c-span do you get it straight from the source . no matter where you're from or where you stand on the issues c-span is america's network. unfiltered, unbiased, word

for word. if it happens here or here or here or anywhere that matters america is watching on c-span, powered by cable. >> jeremy desilva is an f apologist and editor of and is the editor of a most interesting problem: what darling darwin's descent of man got right and wrong about human evolution he's part of the research team that discovered two ancient members of the human family tree , he studied wild bees in western uganda early human fossils in museums throughout eastern in south africa from 1998 to 2003. he worked as an educator at the boston museum of science. kate longest senior editor at scientific american, writing about the evolution of humans and other organisms for the magazine since 1997.

she is co-author with donald johansson of the quest for human origin. tonight they'll be discussing jeremy desilva's new book "first steps: how upright walking made us human". in it desilva explores the history of bipedalism, the ability that makes unique humans unique among other animals to walk on two legs and he makes the case that it allowed for the evolution of humans despite the difficulties imposed on the genome ever after. publishers weekly praises desilva's love of fossil discovery and collaborating with colleagues come through in the wonderful experiences that examiningbones first had . his ability to turn anatomical evidence into a tale of human evolution and his enthusiasm for research would leave readers informed and uplifted. i'm going to turn things over to our speaker

jeremy and kate . >> thank you, i appreciate the introduction. locate. >> great to see you, thanks so much and to the harvard bookstore i'm delighted to have the opportunity to pepper jerry with questions about his new book which is about all the things that i get most excited to write about. it's really a pleasure to be here and i thought maybe jeremy we could sort of take off the conversation by having you tell us why, i mean, humans have a number of traits that separate us from other mammals, other primates. we have naked bodies, large brains and language so white focus on bipedalism? >> is a great question. like you said, we have these differences. we have lots of similarities

to our mammalian cousins and our primate cousins but we have these differences as well. upright walking is one of those. mammals fly and swim and sprints andleap . monkeys walk and climb. your typical mammal moves around on all fours, think about a dog, cat, squirrel moves around on all fours but only humans will navigate the world on their extended hind limbs all the time. it's our very strange way to move and went another mammal does it, we kind of lose our minds. we take out our cameras and videotape and posted to youtube and it gets millions of hits . i was in researching this book i found examples of bears moving on two legs in newjersey . and there have been almost 5 million views of a bear walking on two legs through ov this new jersey suburb. a gorilla in thephiladelphia zoo , lewis and walking on two legs occasionally, not

frequently and someone got a video of it and it ended up on the cbs news. so something that we do all the time, we even use the word pedestrian to describe something ordinary went another animal does it it's remarkable. but not only that, but fossil record which is what i work on, i'mkapparently all oncologists . i study fossils. and what we can tell by going back in time to the common ancestor that we shared with our cousins, the further back we go we start to lose some of these unique characteristics, the large brain, evidence of language, those things happen more recently, stone tools what's the most ancient characteristic we think on our lineage is this ability to move on two legs, so not only is it strange as a metal but it's the most ancient thing that we evolved. it's sort of set our lineage

off and what i argue in the book is that it's was the key innovation that led to many of those other anatomical and behavioral changes that made us human. >> that's a really interesting lens through which to view the entire 80 of human evolution in a sense. this might sound like a weird question but thinking about this from a biomechanics standpoint, upright walking we do it all the time. we take it forgranted . and we don't really think about it. so what is special about it from the standpoint of biomechanics, can you describe the act of walking on two legs and what's unique about it, how do you sort of conveythat ? >> it's a balancing act moving on two legs. think about when i talk to my students about, imagine if i give you an assignment to

design me a chair, you'd probably design it with four legs. and there might be some clever students that make a barstool and make it out of three legs but if you make a chair out of two legs it's probably not going to work and i'm going to sit in it and go all over the student will fail the assignment. to lead locomotion is pretty unusual way than for a metal to move around the world today. we can get into bird locomotion at some point and then deep in the past we find evidence of bipedal is an in dinosaurs and even in an ancient crocodilians lineage which is fun to think about. but from a biomechanical standpoint this is about -p balance. and what we can see and one of the ways we can identify fossils as coming from things that are adapted move on two legs is because they have these specific shapes to them , these individual loans that

would align the joints in a way that would prevent us from tipping over or would change the action of certain muscles so that those muscles would d act in a way to again prevent you from tipping over , one of the classic examples is a hit joint that when you take a step and lift her other leg you fall over. and when a chimpanzee walks on two legs it's exactly what they do, they wobble from side to side. but in humans we evolved our pelvis so here's a human pelvis.lv we've evolved of pelvis where the muscle attachments here have wrapped around the side of the body and binding on the side they then it will interact that every time you take a step. so if you find this part of the body and it looks like this you can tell you have something moving on two legs so kate, you know lucy very well, years lucy's pelvis and sure enough she's got those hip joints arranged in a very

humanlike way. so even if this was the e only part of her we found we y.would be able to tell that she was able to balance on a single leg and what else do that unless you're moving around on twolegs . but from a biomechanical standpoint, and really connecting it to natural selection, it's not a great way to move around your world . we are incredibly unstable on our two legs, we fall a lot. and that can bequite dangerous, there's 30,000 americans who die every year from falling . and in addition to that we are stunningly slow. for a mammal. the fastest human who as far as we know has ever lived, the fastest he ever ran was 28 miles an hour in his hundred meter dash in 2009, his world record 28 miles an hour is impressive and it is,

i couldn't come close to that but it's half the speed of a galloping zebra. after speed of a galloping antelope and perhaps more importantly half the speed of a lion and leopard so evolving this form of locomotion made us slow and so it raises some interesting questions of in what ways was this beneficial? and allowed us to overcome some of those maladaptation's i suppose you can even frame it as just lack of speed. >> you anticipated my next question which is why evolved this, what seems on the surface to be a subpar way of getting around and so i know there's been a lot of scholarship over many decades and with people coming up

with all kinds of ideas about why we could come to how this unusual kind of locomotion and there's some really interesting ideas going back as far as lamarck and darwin and icon it would be fun to take a nickel tour through some ofthose ideas if you wouldn't mind indulging us . >> it's one of those things where if it was another mammal that moved on two legs regularly, we be able to test this more effectively, we be able to do science and say what does this other mammal do, what does it eat or whatever it's mating patterns or what ecology does it live in that in which this form of locomotion is beneficial. so as a scientist when you're trying to figure out something by yourself you always want to out into the natural world and say where else do we see examples like this and the fact that we don't have other mammals that have actually walk around on two legs makes us a really

difficult scientific problems to solve and it's one of the reasons we have insulted in that you can go to lamarck and take it right edup until 2021 people are still hypothesizing why bipedalism was selectively advantageous for our ancestors. you've got ideas of crafts and this goes back to lamarck, he was interested in humans being able to stand and see off into the distance . and with that one, if you look off into the distance and you see a predator the worst way to get away from it would be bipedal he, you'd want to be down on all fours and gallop away because you be muchfaster . so that one hasnever made any sense to me . there are ideas about of course darwin saw this connection between our small canine, are bipedalism and tools. this was about freeing the

hands for tools and that becomes somewhat problematic although i think it's an interesting idea of worth revisiting but because problematic because of the timing that we have evidence for bipedalism in homonyms that are 7 million years old, terrestrial bipedalism and we don't have evidence for stone tools until 3.3 billion years as reported evidence for stone tools and then why wild ideas about displaying genitalia, some sort of showing off of your body for selection, there are ideas that are a little more reasonable and testable having to do with food sharing and if you can free them and not to make weapons or tools but to gather food, there is some ideas that have been promoted where the females are gathering food and sharing it with others, that's nancy cantor's idea

and on lovejoy that argued it's the males that were collecting the sharing it with potential mates. an idea that has had a little maybe more lasting power is energetics, moving on two legs yes we're slow but we are energetically very efficient tand one of the best ways to explain this is herman ponce are and i talked about these ideas and he said that in order to lose a pound of weight you have to walk about 30 miles. because we're too good at it. where to energetically efficient . so now you don't want to lose weight if you're early homonym if you need to get enough food to survive and maybe there's not a lot on the landscape, those individuals who are moving away energetically efficient might survive a little better. so that's possible idea as

well. there are lots and lots of offices. we still don't have a handle on it and that's okay. there are going to be plenty ndof things that new discoveries, new fossil discoveries will allow us to go back and revisit some of these ideas. and really the issue for me is not s.figuring out which one is right, it's beginning to narrow hethe list down to the onesthat are clearly wrong . that's how science works i'm refuting ideas rather than proving them. >> so we don't know yet why bipedalism evil but we do have a lot more information than we used to about the timeframe in which he falls. so maybe we could talk about some of the fossil discoveries that have really

kind of allows you and your colleagues to start to piece together when this all happened. and you know, what it might have evolved from and where it took us. >> a lot of folks listening will probably know about lucy discovered in 1970s and lucy is just a magnificent partial skeleton. i've got the cast of her, the original is in ethiopia of course and not long after lucy was discovered there were footprints found at the site in tanzania where i do some of my research as well. and that pushed idealism back to about 3 and a half million years ago. those were remarkably important discoveries showing humanlike bipedalism existed 3 and a half million and yet the genetics would point point towards a common ancestor we shared with

chimpanzees at about six or 7 million that the split between the two lineages is probably complete by 6 million years, that's a big gap 3 and a half million to 6 million what's going on in that timeframe and in the last 20 years there have been easily remarkable and wonderful and important discoveries that have been made and beginto piece that story together . one is a partial skeleton like lucy from ethiopia that's four and half million years old and it's orthopedic s and article because of some of the key morphologies of the pelvis and the foot. that would indicate that at least and was occasionally able to move around on two legs when it was on the ground that it also has a big grasping tow in the foot so this is an excellent tree climber, long fingers and it's a really good tree climber when it came down to the ground that it not call walk, no, it appears that

didn't and it could actually move on two legs that's 4 and a half million now we get something that's bipedal and as you go further back than that the evidence becomes much more controversial and a little more difficult to interpret. this is toga from a 5 and a half million-year-old homonym from ethiopia and it matches the shape especially the end of the bone of the human tell what was off the ground when you're walking whereas the chimpanzee until actually curves in the ofother direction this has on furniture to it definitely had some time on the trees but it hasn't angulation to it like yours and mine meaning it would probably have been able to push off the ground so this is a cool fossil isjust so , it would be nice to have more .

here's a beautiful fever from kenya that's 6 million years old and what's unique about this one if you compare it to the chimpanzee, here's the chimpanzee . they had or the ball part of a joint is very similar but look how short the net is on the chin and how long that neck is on this fossil. what that would do it's similar to what i was talking about earlier ourepositioning those muscles so you can balance on a single leg bite on those muscles farther from the you're making them more efficient. and we think that anatomy is evidence for bipedal locomotion in what we call fossil from lauren and if we go farther than that 7 million years there's this remarkable soul discovered in chat and it's very controversial, the researchers who founded and first interpreted it argued that the whole base of the

skull abor the spinal cord with a brain was in a very humanlike position and therefore e this creature would have been able to hold itself upright and maybe even walk on two legs. we don't walk with our heads and went to see fossils from other parts of the body and there is a femur now that has been published by one team and another team has a free printout and they come to completely print conclusions on whether this is an upright walker or not. and to me e , as you converge o a common ancestor of humans and chimpanzees you're going to get something that is not quite like any of those living ace and is a fabulous commendation and maybe frustrating commendation of anatomy that is difficult to rinterpret. it's kind of what you might expect in a common ancestor.

>> do you think this femur looks like that of a biped or no? >> i've not been able to ... i like to talk about fossils i've been able to see this is not a fossil i've been able to see myself.and however, there are even older fossils now that are, we don't have much from 8 million, 9 million, 10 million but there's this new discovery from a site in germany and germany sort of like might sound surprising to some of the folks listening because we've been talking about africa but in the late miocene dates expanded all around the mediterranean. what is today the mediterranean and were living in forests of europe so we find a fossils and pain and france and germany, turkey

and hungary. this new fossil from a creature called the new bs from 11 and a half million-year-old deposit in germany looks like it's very upright. and to me that's a really interesting find because could imply and we're still trying to figure this out. it's one of the hottest topics in our field right now of what is the body form from which bipedalism evolved, there are a lot of t-shirts and coffee cups and bumper stickers that would suggest agent turned into a human. and chimpanzees are not our ancestors, they are our cousins . the common ancestor is a that we branch from but so did chimps and chimps have evolved to is not a given that common ancestor was a knuckle walker and some of the fossils that we're finding in those deposits

might indicate that the common ancestor was actually more upright in the trees that knuckle walking could be more derived form of locomotion. there are plenty of researchers, many of my colleagues disagree and think knuckle walking is the form from which bipedalism evolved and they have made compelling cases we need more fossils to figure this out. >> is a revolutionary idea so it's fun to think about that. if bipedalism is a uniquely homonym traits and the new bs at 10 million years old is biped, is he potentially a homonym? >> i don't think so i don't think the timing is right and i think the genetic data showed very clearly when these ages were writing. having said that there are big air marks around these

divergent states but i think you raise an important point that our field has always operated on the assumption that if you find anything that shows characteristics of upright locomotion that it is automatically by definition a homonym meeting it's an ancestor or a relative of us and it would be more closely related to us than any other of the apes. and i think that assumption is on the table. as maybe not being 100 percent correct because if you had in the late miocene apes experimenting with different forms of locomotion including upright asymmetries navigating in the trees they might have some anatomies that look a little more humanlike. for instance the tibia in

some ways looks very much like lucy's. and that is telling us about leg positioning not necessarily weight-bearing on a terrestrial bipedal leg but an animal that's moving with hand assisted bipedalism like orangutans sometimes do, gibbons will do this. spider monkeys will do this. but right, it would mean finding evidence of bipedalism may not be enough anymore to claim hominem status. as we find more fossils from that five, six, seven, eight, 9 million year period we're going to see lots of experiments going on with locomotion and lots of false starts, lots of places where bipedalism may have been

attempted i say but may have evolved and then that animal died out. it just was not a selectively advantageous form of locomotion at but as the habitat changed so we will see, it will be fun. >> we talked a little bit about what the fossil record shows us about the origin of bipedalism but you mention this briefly, there are other r kinds of theories we can look at to sort of study the emergence of this kind locomotion and you mentioned like totally which is a place i've always wanted to visit. it seems like the most iconic site even just thinking about it gives me chills. so there is a very famous set of trapezoid so using

behavior of an animal. and what does that track tell us about the evolution of bipedalism. at that point in time which is 3.6 million compared to what you know about it going back to nubia's for some sort of aurora and. >> it's bipedalism 2.0. it's really good biped, those footprints and that was in 2019 and yes, that place is magical. i think it's just amazing. and there are footprints in all these asked deposits that are eroding out of it besides and like you said, bones, fossilized bones ... i love

fossils and these are wonderful and we can squeeze information out of them and tell stories about what our ancestors were like on the bones but footprints are alive. they're telling you about this moment in time in the life of a living,breathing, thinking individual . >> ... it's not hunched over, crouched down, like a groucho marx walk like a chimpanzee moving on two legs. this is something that from a distance it would look like you and i walking. if you could put it on a treadmill, you would pick up some subtle differences probably and that's a fun thing to think about because you can't ever put an ostrich on a treadmill. let from the footprints and fe

bones it looks like they're not pushing off the big toe quite as much as we do. their arches are little flatter than ours are. their legs are little shorter and they are maybe not extending at the hip quite as much as we do when we walk but those differences are subtle. one of the really i think amazing discoveries of the last ten years is that we often will think of bipedal evolution in a linear way. i even just did it talking about bipedal is in 2.0 but what we see instead are different forms of ip listen evolving in different species. at the same time, lucy and her species were around and her species were making those footprints, there was another species that have a divergent big toe that was in ethiopia not far from where lucy was found,

climbing trees and walking in a different way. this was a fibrous discovery in ethiopia in 2009 and showed there were these different forms of walking coexisting. behind me this skeleton here was discovered by lee berger, actually the first species his nine-year-old son, in in a cn south africa. also in 2009 is when they were published 2008 was the discovery. discovery. i have worked on foot and leg of the skeleton. when i first started working on it, to be i just finished my phd, i had studied the foot and ankle and leg up, noise and homonyms and i seen all these fossils entity there was variation but not functionally meaningful variation and toe the spine. it was different from any item

seen with its heel, it's ankle and it's me and aspects of the hip and the lower back that we have hypothesized that a walk in a very different kind of way that lucy and her kind. what's neat is this carries right up until the pleistocene. even on the doorstep of homo sapiens you have neanderthals in europe, asia, indonesian island and then write in south africa is this brand-new species named in 2015. there were all these different species and populations coexisting. some of them we interbred with. some of them i don't think we probably did, but from the foot bones and the leg boats that looks to me like many of them walked in these biomechanically

slightly different ways, are these different flavors of walking. i left is think about jumping in a time machine and going back to any of these time periods and see these different kinds of us, different species of our ancestors and they wouldn't come they not only would look a little different and may be eating slightly different things but they would be walking a slightly different ways. >> it's really wild to think about that degree in experimentation occurring for the vast majority of human evolution, not just something that happened in the my scene when it was planet of the apes when it was first appearing but right up until virtually yesterday in geological terms. >> that's right. it's amazing. when i was in grad school at the university of michigan the story very much was homo erectus right up to homo sapiens-what we do with neanderthals? fso will argue to that. with a different species or

whether part of our heritage? and now, so to me stating upright walking, the pleistocene wasn't really interesting. we had already evolved so let's go back to the pliocene. the pleistocene is really interesting. there's a lot going on there. >> if we go back to like totally the sort of earliest evidence we have of walking more or less like we do, it's interesting that the first comes of the oldest known stone tools are just a few hundred thousand years younger than those footprints. so we're getting a little bit closer to what darwin was talking about, potentially, right? and i'm wondering sort of like how you see that, how you see

things aligning there. could it be that this bipedalism 2.0 is what frees the hands to start doing stuff like making stone tools? >> i think that possibility again is possible. darwin's ideas, he also incorporated size enlargement which we know now is probably not part of the story that does indeed happen later. but you are absolutely right that if you go back to the 1970s, 1980s we had footprints at 3.6 annual the stone tools at 1.8. and it look like darwin was wrong. and look like the two arches chronologically not aligning. then there were stone tools that are 2.63.6, 2.6, getting closer.

humanlike bipedalism to get pushed back thanks to a tibia discovered by wiki about 4.2 million years old and it's in its very humanlike. i i would love to see what the rest of that creature looks like. honestly, i was going say my hopes, but my expectation given her remarkable my colleagues are a funny these fossils. i love being out there looking for them, but they are much that are fighting them. i think about -- has made extra new discoveries in eastern africa in the last decade or so, the last two decades. so knowing more about that creature i think is going to be really important. but back to your point. we now have at least reports of stone tools at 3.3 million and their controversial.

but at that same time 3.3 million, hasta libidinous means to me behave i'll see any reason why they wouldn't be making stone tools. they are walking like us. they're a slight brain enlargement compared to others about a 20% increase in brain size and there's that new discovery on the basis of a juvenile skeleton that shows they had slowed down brain growth. and slowed down brain growth is tied in mammals to learning and relying for heavily on learning. this is a horrible idea for a slow biped but also something that is going to be heavily predated upon any environment. you would want to speed up your growth rather than slow it down. there were plenty of carnivores on the landscape more than happy to eat so the fact that selection was favoring slow to brain growth to me tells a story

of heavy reliance on learning and learning what? learning how to be and that might have evolved learning how to make stone tools. but it also is a story of cultural buffering and social buffering, that how do you ward off, how do you survive on a landscape like that when you are slow? how do you avoid just been picked off by the leopard all the time? you look out for each other, you have each other's backs. so think our sociology is built into a bipedal locomotion. bipedal locomotion simply is not going to be an evolutionary success unless it happens in something that is either superfast, like an ostrich, or super social, and even compassionate and empathetic like we are. >> i i thought that was a fascinating point that you made

in the book where you start out by talking about early ideas linking bipedalism to violent behavior in homonyms to now you making the argument that actually it could never have worked if our ancestors didn't have the capacity for empathy and cooperation. >> i think so. i think that idea about uprightness, freeing the hands not just for tools but for weapons, is still part of the popular culture. we've all seen 2000 want a space odyssey, right, the beginning there with the wielding of the weapons, and that has its intellectual roots back to raymond dart who discovered the very first, the tongue child who is just over my shoulder here, this wonderful little fossil.

but later in his career in the 1940s post-world war ii he worked at a site where he discovered bones that have been smashed and he formulated a hypothesis that homonyms himself had been doing this, that we were these bloodthirsty killer apes. and that idea has had roots and is still sort of again part of the popular culture, even though we know now that at that site those bones were smashed up because of hyenas. it wasn't us pics of the size has refuted the idea but it still part of how we think about ourselves. and instead, , i draw attentiono a fossil like this discovered in the 1970s by richard leaky and his team in kenya, and this is a leg bone, upper leg bone of the early hominids, about 2 million years old, took that long femoral neck, so we can get some

upright locker, ethical thing about this fossil, amazing thing about this fossil is it has a heel fracture. so this year, this bulge of bone sticking out of the medial side of the inside of the femur, that's a heel fracture. and think about breaking your fever, 2 million years ago, no hospitals, doctors, no fire, no shelter and you break your leg. but you heal? you survive? that can't happen unless other individuals are helping you out. it's not just 2 million. back to lucy species there's a skeleton, a second skeleton and he's about 3.5 million years old, we think it's a large male, and he has a healed ankle fracture. so again he stepped in whole or fell out of a tree, something happened and he broke his ankle. now, if you're a zebra and you

break your ankle, you know, that's not a good situation. but you're still able to get from point a to point b on your three lakes. if you're a biped and you break your ankle, you already slow, and now you're hopping around your landscape, i don't see how you survived. yet this this is a healed . so that individual did survive. and again it's connected in bipedalism that is full of those we have as bipeds but then the fact that we have injuries that make us particularly people if, you know, as bipeds, is again i think explainable only if we were and continue to be empathetic and compassionate and generous and prosocial with one another. >> fascinating. i know we have some questions from the audience that she wants

to put to you. i will turn it over to her. >> thank you. i hadn't heard that about the healed ankle. that's amazing. i had no idea that it went that far back. sorry, that -- >> well, no. that was a discovery, it was a discovery in 2010. >> okay. >> okay, it's 11 years ago now but still it's an indication of just how rapidly my colleagues are finding these fossils and putting them out there. each of these fossils has this amazing story to tell about why we are the way we are today. so it's easy if one, for one to be overlooked. and that one, that's a cool fossil and that was deathly didn't get the attention it deserved. >> yeah, well, while looking through the questions, i feel like the memory that have is

that, the last i heard there was an evidence of that until like later. the idea -- in become sorry. that's awesome. that's nice to know that we can be nicer than we think and goes back longer. that's very reassuring. we have a question from, let's see, if you were able to change human anatomy to make bipedalism easier on us, what would you adjust? >> the foot. the foot is a disaster. i mean, i study feet, and you know, the foot, the foot is sort of like you know evolutions example of a good try. [laughing] you did your best, but what happened here is you converted in a grasping a foot into something that needs to be rigid

and yes, have moments of flexibility but also then pushed off the ground in a rigid way. so have the same 26 bones in our foot that chimpanzees do. so imagine you're trying to create something from scratch and it needs to be able to contact the ground, absorb elastic energy and then kick off the grant into your next step. and to make it out of 26 parts? like, you would fail that engineering course. it just wouldn't happen. look at this. now there you go. >> yes. >> so here's a foot from an ostrich. and what's happened over the course of avian evolution, bird evolution, is that the bones that make up their ankle and foot have fused together into a single, rigid structure that is composed of instead of 26 bones, it's about eight or so in the foot of an ostrich. and this ends up looking a lot

like the blade prosthetic that a lot of para olympians will use and use with great effect and can run very fast. and so yeah, i would totally, i would change the foot. now, now the back is a bit of a mess as well. i work more on the foot and so that's the first place i would go. the knee as a disaster as well. i will stick with the foot. >> kind of two branches off of that. we have another question. do you think, like so the question, it kind of, is it possible for bipedalism in humans or anywhere else to revolve and improve anymore to sort of like do we represent busyness of what this is going to be?

is it even possible to speculate on? >> that's a great question. it's the kind of thing i love to talk questions about, speculate about. i don't think so. if you look in the last 15 at all these different body forms that existed, i don't see the human body today, , homo sapien, setting some advantage over some of those others homo erectus for instance. it looks like the joints were small and so maybe their home range wasn't as large but i certainly don't think that we have reached some pinnacle of bipedal locomotion. and again i would much rather have the skeleton of an ostrich in order to get from point a to point b on two legs. or key racks for that matter. >> right. >> and even if you look back in the past, one of the really fun things i get to research writing this book were bipedal animals that are long gone extinct.

for instance, there's a crocodile discovery in north carolina by vertebrate paleontologist at north carolina state, and she -- at the museum, i'm sorry, at the museum and north carolina. and she reconstructed the gate of this ancient crocodilians is being up on two legs. at least occasionally. so imagine a nine-foot tall crocodile that would jump up on two legs and could spread. right, horrifying. [laughing] and yet what i find fascinating is that didn't have evolutionary legs. you know, what happened to crocodiles? they are all on for next and their ambush hunters pics of being bipedal was not evolutionarily successful boldly. you see that the dinosaurs come to pick the earliest dinosaurs were bipedal. and that okay, apatosaurus and

brontosaurus and brontosaurus and stegosaurus and triceratops come those are quadrupeds that evolved from bipeds. so bipedal is seems to pop up occasionally -- bipedalism -- and honestly fail. and either convert to quadra pedal is in or be a dead into lineage. >> you brought this up in the conversation but maybe just as kind of reminder but like what, so bipedalism arose graduate and sounds like it did. what's the time span, how many millions of years? what's the time span, generally? >> so we don't know. it's really interesting. it depends entirely on what the body form of that common ancestor looked like. because if it was a knuckle walker, if knuckle walking is the ancestral trait and chimpanzees and bonobos have

retained under lynch, guerrillas retained on their lineage, and would have to intense rapid natural selection to go from a knuckle walking common ancestor to something that is not just getting picked off by leopards because it's hunched over and can't move either quickly or efficiently. so it would have in that circumstance either see this happening incredibly fast. or, it happens incredibly slowly. if the common ancestor is something that is imagine more of like a large given with shorter arms or smaller orangutans like think up in the trees moving on two legs and then as there's environmental change and you begin to get past your forest it has to move across the landscape on its two legs but it already has a body formed to do that. and so it's not a new locomotion. it's an old locomotion just in a

new setting. and in that case it would be very gradual and what we would be looking for i think our anatomies that are not from anna boyle by fitbits on the that is a terrestrial biped. we haven't even thought what that would be. as a few. how would you distinguish between something walking on two legs on the ground, very difficult to forces, versus something moving on two legs and assisted bipedalism in the trees where the trees are more compliant. so the forces would be really different. you probably wouldn't have to have those hit mechanics because you are holding your body with your hands and so you will not have that pelvic tilt problem. that something we as a field haven't really grappled with. >> i would think just in contemplating these different scenarios that it would be kind easy to sort fall into a trap about some of these sort of the way, i don't know, maybe by the

time you in your position not come but i don't know. for the layman that wysiwyg would be a pretty easy trap to fall into. >> now, so i'm a darwinian graduate, and i think this probably happens gradually and i think there's probably not when explanation for why bipedalism was selectively advantageous come that it was the host of things in her efforts to sort of the answer is probably pretty wrongheaded. however, so yes, you've got a population in there is variation in the certain individuals that move bipedal he more than others and they end up having more food and more reproductive opportunities and off you go. and we're kind of forget what it is that allows individuals to have more food and reproductive opportunities. there are other scholars that think this was, that this was,

so richard dawkins has written about this, that he thinks bipedalism emerged as sort of a meme, that it was just a cool thing to do, and that chimpanzees, gorillas occasionally move on two legs, and if that sort of became for some reason the fad, and a population, then you could have more and more individuals aping each other, because that's what we do. and because bone is plastic to an extent you might get some of the anatomies that are really key to bipedal locomotion, not because you inherit them genetically but because you are required to them through your life. so the best example of this is at the knee that when you're born your femur is perfectly straight but as you start hobbling around, your femur begins to angle in. you become knock kneed. but we are not born that way.

so when you find a femur as don johansson did in 1973 and it has an angle to it, it tells us that this individual had to walk on two legs because there's no other way to get that angle. so there is this really cool combination of anatomies you're born with and anatomies you acquire that blend together in your musculoskeletal systems allow you to move on two legs. >> man, okay. thank you. we have matthew asking, , what circumstances are making it easier to find more fossils today? >> oh, great question, matthew, great question. select any science you build on the work of previous generations, and there are lots of, you know, false starts that that happened and mistakes made and you learn from the mistakes of predecessors.

but having said that there's also a lot of technological advances that are happening. and so for instance, in south africa one of the reasons my colleague has been able to find as many fossil sites as he has is by using satellite imagery and looking at the clusters of trees that grow out of case. when you're on the landscape walking it's really hard to see these caves, but from the top down you can see them much better. so that's one of the things that's happening. also would argue that the decolonization of the site especially in eastern africa has played a huge role in this, and that instead of doing parachuting signs and drop into displaces and spin a couple weeks and then going back to the united states or back to western europe, a lot of this work now an incredible fossil discovery is being done by individuals that are from those countries.

ethiopia, , tanzania, kenya and many, many others. >> i don't, so kate, i'm curious what you think about that. why do you think we are getting this? >> i mean, the reasons you discover also what it is a a little bit of a stowable effect, like all, lee berger went into like the cradle of humankind which is already supposedly really well explored and found these amazing things. and so maybe we all need to kind of like start going back to places that we thought didn't have any more fossils for us, or that we haven't looked at yet. and you know, kind of go in there with a fresh eye and fresh outlook. >> yeah, i agree. i think that's true. yeah, , that assumption that we

had already, that many of the great discoveries had already been made. you know, the last ten years i have just been astounded by the number of fossils, not just the number. it's not like we are getting more of what we already knew about. that's happening to some degree, but we are also finding, my colleagues are finding things that i don't think any of us could have predicted. i certainly wouldn't have predicted them. so it's been this really wonderful awakening i think in our field, and it does go to humiliate that there is lot out for us still to discover your a lot of our ideas are going to end up being wrong, and that's okay, as long as we are following the evidence, then it's okay to have an idea based on the evidence you have ended

oh, look at this new fossil. it shows i was wrong. oh, well. new fossil. >> i think we should leave it there. i think where out of time. thanks to both of you so much, jeremy and kate. thank you for this fantastic and thank you for joining us. please learn more about this incredible book. i posted a link in the chat harvard.com/book pictures also link up there to donate. thanks so much for tuning in, and stay safe. have a lovely night and thanks again to both of you. >> american history tv saturdays on c-span2 exploring the people and events that tell the american story. at 12:30 p.m. eastern on the presidency house speaker nancy pelosi along with the missouri congressional delegation unveil a bronze statue of harry truman

to the u.s. capitol rotunda. 1:30 p.m. eastern to mark the 50th anniversary of the return of american pows from vietnam in 1973 author talks about their harrowing experience and the work of the national league of pow/mia families to bring them home. exploring the american story. watch american history tv saturdays on c-span2 and find a ll schedule on your program guide or watch online anytime at c-span.org/history. >> middle and high school students it's your time to shine. you are invited to be suspect in this year's csp's studentcam documentary competition. in light of the upcoming midterm elections picture yourself as a newly elected member of congress. as this year's competitors what is your top priority and why. make a five to six minute video that shows the importance of your issue from opposing and supporting perspective.

don't be afraid to take risks with your documentary. be bold. amongst the $100,000 in cash prizes is a $5000 grand prize. videos must be submitted by jenner 20, 2023. visit our website at studentcam.org for competition rules, tips, resources and a step-by-step guide. >> there are a lot of places to get political information, but only at c-span2 you get it straight from the source. the matter where you are from or where you stand on the issues, c-span is america's network. unfiltered, unbiased, word for word here if it happens here or here or here, or anywhere that matters, america's watching on c-span. powered by cable. >> host: governor kristi noem, i'm going to rip the band-aid off and get right to some of the topics you may not want to